INT-201: Computer Network and Communication System

INT-201:Computer Network and Communication System Module1: Introduction อ.ดร. ภัทร ลีลาพฤทธิ์ Dr. Pattara Leelaprute Computer Engineering Department Kasetsart University pattara.l@ku.ac.th http://www.cpe.ku.ac.th/~pattara/int201 Computer Networking: A Top Down Approach ,4th edition. Jim Kurose, Keith RossAddison-Wesley, July 2007. Introduction

Outline • Introduction to Computer • Operating System • What is Internet? • Network structure • The Network Core Introduction

Definition of Computer • Devices for performing computations at high speeds with great accuracy • A machine that can be programmed to manipulate symbols • Physical components are known as “Hardware” Introduction

Where to find Computer? • Home • Business • School • Where else? Hospital, automobiles, aircraft, electronic appliance, mobile phone, etc… Introduction

Computer Systems • Hardware (HW) • Actual physical machines (equipment) that make up the computer (e.g. monitor, keyboard) • Software (SW) • Programs written for a specific application are often called software (e.g. Window XP, Linux, Microsoft word) Introduction

Computer Categories • Personal Computer • Desktop Computer • Notebook • PDA – Personal Digital Assistant • Supercomputer  Mainframe • High Computation Power • Server • Workstation Introduction

Server & Workstation Introduction

Computer Components • Input Devices • Output Devices • Computing & Processing Unit Introduction

Secondary Memory (DVD, FDD, HDD) CPU Main Memory Output Devices HD Computer Components (details) Input Devices *CPU= Central Processing Unit Introduction

Computer Components (pictures) Hard disc CPU Introduction

Computer Memory Can be divided into 2 Categories • RAM (Random Access Memory) • ROM (Read Only Memory) • Memory in Computer • Main Memory • Secondary Memory Introduction

Main Memory Much faster More expensive Volatile (Temporary) Secondary Memory Slower Less expensive Permanent Main Memory VS Secondary Memory Introduction

1. Main Memory • Memory Cell -> Byte -> bit • 1 Byte = 8 bits Introduction

2. Secondary Memory • Floppy disk • Hard disk • CD-ROM, CD-R, CD-RW • DVD-ROM, DVD-R, DVD-RW • Blu-ray disc Etc… Introduction

Data Representation • Data in computer is represented in “bit” • bit = binary digit • 0 or 1 • Byte = 8 bits • 1 byte can represent many kids of data • 1 byte = 011000012 • the above 1 byte means, 97 or “a” in ASCII code • ASCII=American Standard Code for Information Interchange. • the meaning of 1 byte depends on the program • Photos, Voice, Video, etc 1 Kbyte = 210 = 1024 bytes (KB) 1 Mbyte = 220 = 1,048,576 bytes (MB) 1 Gbyte = 230 = 1,073,741,824 bytes (GB) 1 Tbyte = 240 = 1,099,511,627,776 bytes (TB) Introduction

ASCII code • 8bit code for character representation (7 bits plus parity) • 0-127 represents the letter of alphabet, numbers and symbols Introduction

Binary and Decimal • How to convert binary to decimal? 1 0 0 1 1 2 = ? 2 5 5 1 10 = ? 2x103 + 5x102 + 5x101 + 1x100 1 0 0 1 1 2 = 1x24 + 0x23 + 0x22 + 1x21 + 1x20 1 0 0 1 1 2 = 24 + 21 + 1 = 16+2+1 = 19 How to convert decimal to binary ? Introduction

Boolean Expression • And • Or • Not 0 and 0 = 0 0 and 1 = 0 1 and 0 = 0 1 and 1 = 1 0 or 0 = 0 0 or 1 = 1 1 or 0 = 1 1 or 1 = 1 not 0 = 1 not 1 = 0 Introduction

Type of Application • Local application • Program, such as a word processor, that is stored on the hard disk of the computer. • The application runs only on that computer. • Network application • Program that is designed to run over a network, such as the Internet. • A network application has two components, one that runs on the local computer and one that runs on a remote computer. • ex., Email Introduction

Ex., RAM, Hard disk, CPU Operating System (OS) • Software component of a computer system • Responsible for the management and coordination of activities and the sharing of the resources of the computer. • All computerized devices, such as servers, desktops, laptops require an OS • ex. Microsoft Windows, MAC OS X, Linux, Unix Introduction

Operating System (OS) • What does OS do? • Program execution • Memory management • Multitasking • Disk access and file systems • Device drivers (printer, monitor) • Input/Output • Networking • Let’s think about WORD application. • Write a report and print it out. • OS collaborates keyboard, monitor, hard disk, and printer. Introduction

User Interface (for OS) • Command line interface (CLI) • Graphical user interface (GUI) CLI Introduction

Quiz • ((1 and 0) or (1 and 1)) = ? • What is I/O device ? • What is RAM and ROM ? • 1 byte = xxx bits • 1 Mbyte = xxx byte • 10000102 = ? Introduction

millions of connected computing devices: hosts = end systems running network apps PC Mobile network server Global ISP wireless laptop cellular handheld Home network Regional ISP access points wired links Institutional network router What’s the Internet: overview • communication links • fiber, copper, radio, satellite • transmission rate = bandwidth • routers: forward packets (chunks of data) Introduction

“Cool” internet appliances Web-enabled toaster + weather forecaster IP picture frame http://www.ceiva.com/ World’s smallest web server http://www-ccs.cs.umass.edu/~shri/iPic.html Internet phones Introduction

protocolscontrol sending, receiving of msgs e.g., TCP, IP, HTTP, Skype, Ethernet Internet: “network of networks” loosely hierarchical public Internet versus private intranet Internet standards RFC: Request for comments IETF: Internet Engineering Task Force Mobile network Global ISP Home network Regional ISP Institutional network What’s the Internet: “nuts and bolts” view Introduction

communication infrastructure enables distributed applications: Web, VoIP, email, games, e-commerce, file sharing communication services provided to apps: reliable data delivery from source to destination “best effort” (unreliable) data delivery What’s the Internet: a service view Introduction

human protocols: “what’s the time?” “I have a question” introductions … specific msgs sent … specific actions taken when msgs received, or other events network protocols: machines rather than humans all communication activity in Internet governed by protocols What’s a protocol? protocols define format, order of msgs sent and received among network entities, and actions taken on msg transmission, receipt Introduction

a human protocol and a computer network protocol: TCP connection response Get http://www.awl.com/kurose-ross Got the time? 2:00 <file> time What’s a protocol? Hi TCP connection request Hi Q: Other human protocols? Introduction

network edge: applications and hosts (send-receive msg) Network structure: • access networks, physical media: wired, wireless communication links • network core: • interconnected routers • network of networks Introduction

end systems (hosts): run application programs e.g. Web, email at “edge of network” peer-peer client/server The network edge: • client/server model • client host requests, receives service from always-on server • e.g. Web browser/server; email client/server • peer-peer model: • minimal (or no) use of dedicated servers • e.g. Skype, BitTorrenth Introduction

Goal: data transfer between end systems handshaking: setup (prepare for) data transfer ahead of time Hello, hello back human protocol set up “state” in two communicating hosts TCP - Transmission Control Protocol Internet’s reliable data transfer service TCP service[RFC 793] reliable, in-order byte-stream data transfer loss: acknowledgements and retransmissions flow control: sender won’t overwhelm receiver congestion control: senders “slow down sending rate” when network congested Network edge: reliable data transfer service Introduction

Goal: data transfer between end systems same as before! UDP - User Datagram Protocol [RFC 768]: connectionless unreliable data transfer no flow control no congestion control App’s using TCP: HTTP (Web), FTP (file transfer), Telnet (remote login), SMTP (email) App’s using UDP: streaming media, teleconferencing, DNS, Internet telephony Network edge: best effort (unreliable) data transfer service Introduction

Q: How to connect end systems to edge router? residential access nets institutional access networks (school, company) mobile access networks Keep in mind: bandwidth (bits per second) of access network? shared or dedicated? Access networks and physical media Introduction

Dialup via modem up to 56Kbps direct access to router (often less) Can’t surf and phone at same time: can’t be “always on” Residential access: point to point access • DSL: digital subscriber line • deployment: telephone company (typically) • up to 1 Mbps upstream (today typically < 256 kbps) • up to 8 Mbps downstream (today typically < 1 Mbps) • dedicated physical line to telephone central office Introduction

HFC: hybrid fiber coax asymmetric: up to 30Mbps downstream, 2 Mbps upstream network of cable and fiber attaches homes to ISP router homes share access to router deployment: available via cable TV companies Residential access: cable modems Introduction

Residential access: cable modems Diagram: http://www.cabledatacomnews.com/cmic/diagram.html Introduction

company/univ local area network (LAN) connects end system to edge router Ethernet: 10 Mbs, 100Mbps, 1Gbps, 10Gbps Ethernet modern configuration: end systems connect into Ethernetswitch LANs: chapter 5 Company access: local area networks Introduction

shared wireless access network connects end system to router via base station aka “access point” wireless LANs: 802.11b/g (WiFi): 11 or 54 Mbps wider-area wireless access provided by telco operator ~1Mbps over cellular system (EVDO, HSDPA) next up (?): WiMAX (10’s Mbps) over wide area Wireless access networks router base station mobile hosts Introduction

Typical home network components: DSL or cable modem router/firewall/NAT Ethernet wireless access point Home networks wireless laptops to/from cable headend cable modem router/ firewall wireless access point Ethernet Introduction

Bit: propagates betweentransmitter/rcvr pairs physical link: what lies between transmitter & receiver guided media: signals propagate in solid media: copper, fiber, coax unguided media: signals propagate freely, e.g., radio Twisted Pair (TP) two insulated copper wires Category 3: traditional phone wires, 10 Mbps Ethernet Category 5: 100Mbps Ethernet Physical Media Introduction

Coaxial cable: two concentric copper conductors bidirectional baseband: single channel on cable legacy Ethernet broadband: multiple channels on cable HFC Physical Media: coax, fiber Fiber optic cable: • glass fiber carrying light pulses, each pulse a bit • high-speed operation: • high-speed point-to-point transmission (e.g., 10’s-100’s Gps) • low error rate: repeaters spaced far apart ; immune to electromagnetic noise Introduction

signal carried in electromagnetic spectrum no physical “wire” bidirectional propagation environment effects: reflection obstruction by objects interference Physical media: radio Radio link types: • terrestrial microwave • e.g. up to 45 Mbps channels • LAN (e.g., Wifi) • 11Mbps, 54 Mbps • wide-area (e.g., cellular) • 3G cellular: ~ 1 Mbps • satellite • Kbps to 45Mbps channel (or multiple smaller channels) • 270 msec end-end delay • geosynchronous versus low altitude Introduction

mesh of interconnected routers the fundamental question: how is data transferred through net? circuit switching: dedicated circuit per call: telephone net packet-switching: data sent thru net in discrete “chunks” The Network Core Introduction

End-end resources reserved for “call” link bandwidth, switch capacity dedicated resources: no sharing circuit-like (guaranteed) performance call setup required Network Core: Circuit Switching Introduction

network resources (e.g., bandwidth) divided into “pieces” pieces allocated to calls resource piece idle if not used by owning call (no sharing) Network Core: Circuit Switching • dividing link bandwidth into “pieces” • frequency division • time division Introduction

INT-201: Computer Network and Communication System